The company, which allows users to take unlimited fitness classes for $99 a month, has raised more than $54 million, is currently in 34 markets and just acquired competitor FitMob, for an undisclosed amount, TechCrunch reports.

Both services buy discounted classes from a growing number of boutique fitness studios and gyms, and then allow their members to sign up for individual sessions through a subscription service. It's a model that's proven wildly successful: ClassPass, a graduate of Techstars NYC's 2012 spring class, is rapidly growing (since early 2014, co-founder Payal Kadakia says the company has doubled its user base every three months).

That wasn't always the case, however. Originally conceived as a database to book individual classes, fewer than 100 classes were booked on ClassPass's platform in its first year. It was only after the company pivoted away from its Open Table, a la carte model to an all-you-can-eat buffet subscription service that things took off.

ClassPass is far bigger than Fitmob, which was operating in eight markets; According to TechCrunch, Fitmob members will automatically become ClassPass subscribers.

This acquisition, ClassPass's first, emphasizes the large impact the company has had on the high-end fitness market in a relatively short period. But while consumers are flocking to the service, it remains to be seen if its system of studios can handle the influx. (Anecdotally, friends in New York have reported having a difficult time reserving the classes they want as the service has become more popular.) In addition, some studios have pushed back, arguing that selling discounted classes to the company is an unsustainable business model.